1. Field of the Invention
The invention relates to a method for charging particles by charging the particles in a friction charger and subsequent separation.
The invention further relates to a device for carrying out the method.
2. Discussion of Background
In the electrostatic separation of particles, for example coal particles, finely ground particles are charged in a friction charger (TRIBOcharger) by collisions with solid bodies, for example walls. Friction chargers of this type are described, for example, in the brochure "ESB Electrostatik-Automatik-Pulverbeschichtungs-Systeme" (ESB Electrostatic Automatic Powder-coating Systems), page 13, from the firm ESB, Meersburg (FRG), undated. This charging depends strongly on the dielectric characteristics of the particles. A good insulator will be differently charged in this case than a poor insulator, so that the good insulator material can be separated from the poor insulating material in an electric field. Depending on the combination of the materials to be separated it is even possible for chargings of different polarity to occur. Further charges are brought onto the particles by a plurality of collisions; however, the number is no longer as large as in the case of earlier collisions, because saturation is finally achieved. The aim of the efficient friction chargers is to achieve this "maximal" charge density by as few collisions as possible.